Every signal transduction pathway requires a _____, most commonly an integral membrane protein, that specifically binds a small molecule called a _____.
Receptor; ligand.
What is a receptor?
A molecular structure on the surface or interior of a cell that binds with substances such as hormones, antigens, drugs, or neurotransmitters.
Which of the following statements concerning receptors is CORRECT?
A.) They have an active site on the extracellular side of the membrane.
B.) They contain an enzyme activity for which the signal molecule is a substrate.
C.) They have a ligand binding sit
C.) The have a ligand binding site on the extracellular side of the membrane.
Which of the following statements concerning receptors is FALSE?
A.) Receptors bind signal molecules specifically and irreversibly.
B.) Receptors bind the first messenger at a specific binding site on the extracellular side of the cell membrane.
C.) Recep
A.) Because Receptors interact with their ligands in a reversible manner.
What is a ligand?
A molecule that binds to the active site of a receptor.
Hormones bind to _____ with _____ affinity.
A.) agonists; high
B.) antagonists; low
C.) ligands; low
D.) G proteins; low
E.) receptors; high
E.)
A receptor interacts with its ligand in such a way that some kind of response occurs _____.
Inside the cell.
What are two kinds of ligands?
- Agonist: A ligand that binds to a receptor and elicits response from the cell.
- Antagonist: A ligand that binds to a receptor but does not elicit a response from the cell.
Caffeine is an _____ of the adenosine receptor because it binds to the receptor but does not trigger a response.
Antagonist; as a result, caffeine keeps the heart rate high and produces a sense of wakefulness.
Signaling molecules behave much like enzyme substrates in that they?
They bind to their receptors with high affinity, reflecting the structural and electronic complementarity between each ligand and its binding site.
Receptor-ligand binding can be written as a _____ reaction such as?
Reversible;
R + L <==> R x L
How is the affinity of a ligand binding to a receptor (Kd) characterized?
Kd = [R] [L] / [R x L]
Kd- is the ligand concentration at which the receptor is half-saturated with ligand.
- Low values of Kd indicate a strong binding (high affinity).
As the ligand concentration [L] increases, more receptor molecules bind ligand. Therefor, receptor-ligand binding is _____.
Hyperbolic
Sample of cells has a total receptor concentration of 28mM and 33% of the receptor are occupied with ligand. The concentration of free ligand is 11mM. Calculate Kd.
Kd = [R] [L] / [R x L]
- L is free ligand, 11mM
- [R x L] is found multiplying 28mM by 0.33.
- R is found by subtracting the answer for [R x L] from 28.
Kd = [18.76] [11mM] / [9.24]
Kd = 22.33 mM
Most signaling occurs through what two types of receptors?
1. G proteins
2. Kinases
What is a G protein?
In response to receptor ligand binding, the G protein becomes activated and in turn interacts with and thereby activates additional intracellular proteins. They are often an enzyme that generates a small molecule product that diffuses through the cell cal
What are second messengers?
Signaling molecules generated inside of the cell as a response to extracellular stimuli.
Which of the following is never a second messenger?
A.) A lipid.
B.) A calcium ion.
C.) A nucleotide.
D.) A protein.
E.) A carbohydrate derivative.
D.) a protein
What are Kinases?
Enzymes that take a phosphate from ATP and put it on a substrate.
Which of these statement about second messengers is false?
A.) Second messengers helps with the propagation of the signaling pathway
B.) Second messengers amplifies the signal
C.) Second messengers is typically short lived
D.) They can function as a feed
E.) second messengers are more like a small molecule ligand.
G-protein coupled receptors include _____ transmembrane helices.
Seven
The physiological ligands for the B-adrenergic receptor are what?
The hormones epinephrine and norepinephrine, which are synthesized by the adrenal glands from the amino acid tyrosine.
Which of the following is NOT a general component of a signal transduction pathway?
A.) First messengers (ligand).
B.) The cell (plasma) membrane.
C.) G proteins.
D.) Receptors
E.) Target proteins (enzymes).
C.) G proteins
Which of the following does NOT occur in biological signaling systems?
A.) Opening or closing of ion channels.
B.) Autophosphorylation.
C.) Protein-protein interactions.
D.) All of the above processes may occur.
E.) Ligand-protein interactions.
D.) All of the above
The substances epinephrine and norepinephrine are sometimes called _____ and _____, also function as _______ and are responsible for what?
Adrenaline and noradrenaline;
Neurotransmitters;
The fight-or-flight response.
What is the fight-or-flight response characterized by?
Fuel mobilization, dilution of blood vessels and bronchi, and increased cardiac action.
Your adrenal gland is located on top of which organ?
Kidneys
The two neurotransmitters associated with fight or flight response are?
Epinephrine and norepinephrine
Which of these symptoms is not associated with the fight or flight responses?
A.) Sweating
B.) Pupil dilation
C.) High blood pressure
D.) Drowsiness
E.) Increased heart rate
D.) Drowsiness
B2-adrenergic receptor is a G protein coupled receptor with _____ transmembrane helices.
Seven
What are the steps of the signaling mechanism of B-adrenergic receptors?
1. The binding of the LIGAND cause a conformation change within the receptor that exposes a binding site on the CYTOSOLIC side of the receptor.
2. The exposed binding site ATTRACTS G-protein complex and cause it to exchange its bound GDP for a GTP.
3. Thi
The binding of G-protein complex to the receptor causes what?
Causes it to exchange GDP for a GTP.
What is a major target of activated G protein?
Adenylate cyclase
_____ generates the second messenger cyclic AMP.
Adenylate cyclase
cAMP activates _____. The level of cAMP determines the level of activity of _____.
Protein Kinase A;
PKA or Protein Kinase A.
Some of the responses related to the activation of B2-adrenergic receptors are?
1. Increased heart rate
2. Increased blood pressure
3. Intestine movement slows down
4. Decrease output of digestive enzymes
What type of secondary structure predominates in GPCRs?
A.) Alpha helices
B.) Beta sheets
A.) 7 alpha helices
When epinephrine or norepinephrine binds to the b2-adrenergic receptor this induces
A.) An action potential
B.) A conformational change on the extracellular region of the receptor
C.) Opening of the sodium channel
D.) A conformational change on the intrac
D.) A conformational change on the INTRACELLULAR region of the receptor.
When bound it is very hard for a receptor to let go of its natural ligand.
A.) True
B.) False
B.) FALSE, you need to shut off signal eventually.
The quaternary structure of G protein is?
A.) Homo-dimer
B.) Mostly alpha helices and irregular secondary structure
C.) Hetero-tetramer
D.) Hetero-trimer
E.) A propeller domain
D.)
The subunit of G-protein that binds to GDP and GTP is?
A.) Alpha
B.) Beta
C.) Gamma
D.) Regulatory domain
E.) Catalytic domain
A.) Alpha
One of the reasons activated G-protein can find adenosine cyclase quite easily is because?
A.) They are both kinases
B.) They are both next to the nucleus
C.) They are both membrane bound
D.) They are both bound to the same substrate
E.) They have opposit
C.) Diffuses only along membrane, anchored.
Because adenosine cyclase is an enzyme, what it its order of rate constant?
A.) Zero
B.) First
C.) Second
D.) Third
E.) Forth
C.) Second
Beta blockers are common medication given to patient with high blood pressure. Do you think they function as agonist or antagonist of G-protein coupled receptor?
Beta blocker is an ANTAGONIST of adrenergic receptors.
Which of these statements accurately describes how PKA is activated?
A.) A conformational change exposed a binding site
B.) Activated by PKB
C.) cAMP binding cause the release of catalytic subunits from regulatory subunits
D.) cAMP binding cause the compl
C.)
In addition to regulation by cAMP binding to the R subunit, protein kinase A itself is regulated by what?
Phosphorylation
G-protein complex resets itself by the _____ activity of the a subunit.
GTPase
cAMP has a short lifespan due to the degradation by _____.
Phosphodiesterase
Caffeine, in addition to being an adenosine receptor antagonist, can do what?
Can diffuse inside cells and inhibit cAMP phosphodiesterase. As a result, the cAMP concentration remains high, the action of protein kinase A is sustained, and stored metabolic fuels are mobilized, readying the body for action rather than sleep.
What are the steps of the signaling mechanism of a-adrenergic receptor?
1. Ligand BINDING on the receptor cause a conformational change which exposes a binding site on the CYTOSOLIC side of the receptor.
2. The binding site interacts with the G-protein complex cause it to EXCHANGE the bound GDP for a GTP.
3. The exchange of g
What are some of the responses related to the activation of a-adrenergic receptor?
1. Constriction of blood vessels.
2. Relaxing of smooth muscles.
3. Sweating
What makes a-adrenergic receptor different from B-adrenergic receptor?
A.) a-adrenergic receptor interacts with G-protein and b2-adrenergic receptor interacts with adenylate cyclase
B.) a-adrenergic receptor goes through conformational change prior to act
ANSWER IS C.
- A is wrong because they both interact with G-protein.
- B is wrong because they have the same receptor, both go through ligand binds on the intracellular side.
- D is wrong because Beta uses cyclic amp and not alpha.
- E is wrong because ep
Phospholipase C cleaves Phophatidylinositol biphosphate (PIP2) generating what?
IP3 + DAG (inositol trisphosphate and diaclyglycerol.
The action of phospholipase C results in the formation of 2 second messengers. Which of these are lipid-soluble?
A.) Inositol trisphosphate
B.) Diaclyglycerol
B.) It is soluble and floats through the cell and binds to calcium channel.
The human growth hormone receptor is a receptor _____.
Kinase
What are the steps of the mechanism of receptor tyrosine kinase (Ras)?
1. Ligand binding on the receptor causes DIMERIZATION of the receptor which induces AUTOPHOSPHORYLATION of the activation loop.
2. With its tyrosine residues phosphorylated, the activation loop move out of the way to expose the ACTIVE SITE.
3. This facili
What are some of the responses related to the activation of receptor tyrosine kinase (RAS)?
1. Cell division
2. Cell growth and remodeling
3. Cell death
4. Cell differentiation
5. Cancer when mutated
What is a crosstalk?
When the response of one signaling pathway feed into another pathway.
Which of the two types of cellular receptors possesses direct catalytic activity?
A.) G-protein coupled receptors
B.) Receptor tyrosine kinases
B.) Tyrosine kinase are able to phosphorylate each other.
Signal transduction can be mediated by two different types of receptors that use different pathways of activation. What do they share in common?
A.) They are all transmembrane proteins.
B.) The process begins with a conformational change induced by ligand
D.) Only G protein interact with G protein, and tyrosine kinase does not.
Which of the following statements about the receptor tyrosine kinase is TRUE?
A.) It can autophosphorylate
B.) Ligand binding induces conformational change
C.) it require G-protein
D.) A and B
E.) A and C
D.)
Which of the following components of the receptor tyrosine kinase pathway are NOT enzymes?
A.) The receptor
B.) G protein
C.) Ras protein
D.) Protein kinases
E.) Adaptor proteins
E.) Adapter protein does NOT have any catalytic activity.
The interaction of various signaling pathways is called?
A.) Desensitization
B.) Cross-talk
C.) Signal transduction
D.) Dual-specificity
E.) Auto-inhibition
B.) Cross-talk
What is a lipid (steroid) hormone?
Signaling molecules that are made up of mostly hydrocarbons (CH2)n.
What is the solubility property of lipid hormones? What does its solubility mean?
It is hydrophobic, meaning it can go through cell membrane but needs a chaperon protein in the blood stream, albumin.
Some hormones are lipids that _____ to receptors. Examples?
Do NOT bind to receptors. Cortisol, retinoic acid and thyroid hormones thyroxine and triiodothyronine.
Some receptors are _____ which function as transcription factors so that the genes near the hormone response elements may experience higher or lower levels of expression.
Transcription factors
The hormone response elements are all composed of what?
Two identical 6-bp sequences separated by a few base pairs that can only be bound when the hormone receptors are dimerized.
What are the steps of the mechanism of lipid hormone signaling?
1. The hormone enters the cell through diffusion because it is lipid soluble.
2. Inside the cytosol it binds to the hormonal receptor and causes it to dimerize.
3. The dimerized receptor enters the nucleus and binds to the hormone response element and tur
Which of the following statements regarding lipid hormone signaling is FALSE?
A.) Lipid hormones can enter the cell through simple diffusion.
B.) Lipid hormones bind to cell surface receptors.
C.) Lipid hormone receptors function as transcription factors.
B.) Is FALSE BECAUSE lipid hormones bind to the receptor inside the cell.
Which of the following pathways would provide the slowest response to an extracellular signal?
A.) Phosphorylation events
B.) Activation through second messengers
C.) Lipid hormone mediated control of gene expression
C.) ex: muscle builder would take a while for results.
What is a hormone response element?
A.) A hormone receptor
B.) It is activate a hormone receptor
C.) Is a DNA sequence that is regulated by the hormone receptor
D.) Is a kinase that is regulated by the hormone receptor
E.) The element on the periodic tabl
C.) A hormone response element is a DNA sequence that is regulated by the hormone receptor.
The reason the hormone response element is made a two identical DNA sequence is because?
A.) The activated receptor is a homo-dimer
B.) The inactive receptor is a homo-dimer
C.) They have to be complementary
D.) The hormone that activates it is a homo-dim
D.) The hormone that activates it is a homo-dimer.
The reason steroids can be injected directly into the muscle is because
A.) Muscle has G protein receptor on its surface
B.) Muscle has receptor tyrosine kinase on its surface
C.) Muscle has hormone response element on its surface
D.) Steroids can diffuse
D.) Steroids can diffuse through the cell membrane.